Study: Babies can 'tune in' faces

Infant's-eye view may be clue to the developing brain

Six-month-old babies were better than 9-month-olds, and even better than adults, at distinguishing between monkey faces.

(CNN) -- Because of the way human brains develop, 6-month-old babies are better at recognizing certain faces than 9-month-old infants. Even more surprising, those 6-month-old babies are also better than adults at some face recognition.

The catch? -- the 6-month-olds excel at recognizing non-human faces.

In a study detailed in Science magazine, researchers discovered that the 6-month-olds had no problem distinguishing between people, or between monkeys. But just three months later, at 9 months of age, babies could still tell the difference between human faces, but they couldn't tell one monkey from another.

"Here's what we think is going on," says Charles Nelson, child psychologist at the University of Minnesota. "Early in development, the brain is open to any face." But, he says, apparently sometime between 6 and 9 months of age, babies' brains key in on the fact that human faces are the ones to which they need to pay attention.

"It's one way of looking at the bigger question of how brains develop into the adult-like form," says Michelle de Haan, a co-author of the study working at the Institute of Child Health at University College in London. "When babies are born, do they already have this little face-and-language area? Do they have areas dedicated to specific functions?"

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Nelson and de Haan say it's possible that both natural changes in the brain between 6 and 9 months -- plus the variety of visual cues from the environment -- work together to create recognition capabilities.

Nelson says that as we get older, we get better at detecting the subtle differences in the faces we see a lot: human faces. But at the same time, we lose the ability to detect differences in things we don't see a lot. It's a phenomenon called "cognitive narrowing."

Olivier Pascalis, who led the study at the University of Sheffield in England, says a baby's brain gets "hard-wired" during the first year of life, creating a template it can use to compare all those new human faces.

The researchers say there may be some overlap in how face recognition develops, and how speech recognition develops. Nelson says that may be why young children can learn a second language more easily than adults.

How do you test babies?

This study involved 30 6-month-olds, 30 9-month-olds and 11 adults. In studies like this, the babies look at pictures while sitting on adults' laps. Researchers videotape the children's eye movements to gauge which picture they're focusing on and for how long. Babies of any age, as well as adults, will look longer at a picture that's new or unfamiliar.

Humans of all ages tend to focus longer on images that are new and unfamiliar.

Participants were first shown identical pictures -- either two monkeys or two humans. Then, they were shown one of those original pictures again, plus a new photo.

When looking at the monkey pictures, the 6-month-olds spent more time looking at the new picture. But the 9-month-olds, as well as the adults, split their time pretty evenly looking at the two monkey faces. Researchers say this means they didn't recall seeing one of the monkey faces earlier. Those in every age group could tell the difference between new human faces and human faces they had seen before.

Adult brains are not so rigid that they stop learning certain things after a certain age -- it's just a bit harder. Adults can learn new languages. They can even distinguish among a lot of monkeys if they spend time working with or caring for those or other animals.

What else can scientists learn from such studies? Nelson says that knowing more about what parts of the brain are key to skills like speech and face recognition could help in the diagnosis and treatment of developmental delays or difficulties.